thanks a lot for the reply, in this project I've to use a magnetic head, not a pre-built reader so I'll have no clock data but that on the track itself, the encoding that I'll be dealing with (when I'm able to retrieve the F2F signal and the binary from that) is the ABA of the middle track of a credit card, however I've assemble the circuits on this forum and the one of this application note:http://www.eettaiwan.com/ARTICLES/2001OCT/PDF/2001OCT04_AMD_CT_AN2112.PDFHowever with both I'm having problems, the first (the one on this forum) the output changes from 0 to 1 even though I'm not swiping and when I pass the card it does nothing, the second one stays low all the time, and the voltages that I get are not the ones for the stable state presented in the app note, but I've built it three times from scratch with the same result every timeMy magnetic head is working 'cause if I swipe it i can see the signal after amplification, however I'm unable to transform that signal to a F2F encoded wave

Hi i meant the comparator of the circuit that was posted here on the topic, it's the second post, as far as for the PDF I know it has no components, but I assemble it with real components and it doesn't work, I don't know what can be wrong since it's just amplifiers and comparators, and i test each of the part separately and all is working it's just that it doesn't give the voltages for the steady state that the pdf shows, and I think that i can wire it fine, so I don't know what can be =S

Of the other circuit that i mention (the one posted here) if you check it the comparator has a wire from the (-) input to the output through a resistance, that's what i call retro and on a comparator I have never seen one (at least that I remember)

I know it has no components, but I assemble it with real components and it doesn't work,

Yes that is why I was asking for the schematic of what you are trying to make with real components an part numbers to see if you had made a mistake with the conversion into a real circuit. There could be a problem with the type of op amp you are using, the feedback components or anything, but just saying it doesn't work is not very conducive to trying to find out what is wrong.Basically it is a digital circuit but made with analogue blocks of that anadigm device. So you could just as easily do it in the digital domain.

I suspect however that you are not even getting a signal out of the first amplifier, do you have a scope you can measure things with?

It is already in binary, that is how it is stored in the computer. When you print it out it is converted to decimal.Exactly what do you want to do with the number? If it is just to print it the look at the serial.print in the reference and see what you need to add to get it to output in binary.

No because what you need here is a comparator to detect a threshold value or not.All an A/D will give you is a number that you will have to compare against to get a binary value. The same effect can be had by simply varying the gain of the amplifier.